Battery packs have become an essential facet of modern technology for consumer, automotive, medical, computing and industrial products. Battery management systems, including so-called battery fuel gauges or gas gauges, are used to control the charging and discharging of battery cells within a battery pack, to perform cell balancing operations, as well as to provide estimates of remaining battery cell capacity. Battery cells are often connected in series configurations to provide the necessary voltages required by specific applications. More recently, asymmetric battery stacks have been proposed for automotive and other applications in which the individual cells forming the battery pack are of different capacities to facilitate increased pack capacities while making the best use of limited end equipment chassis space. However, asymmetric battery stacks present difficulties for cell balancing, where conventional voltage equalization type balancing techniques are not optimal, and fairly large bypass current levels are sometimes needed. Accordingly, a need remains for improved apparatus and techniques for managing battery packs.